The invention concerns a method and a device for treating and processing flat substrates, in particular silicon wafers, for the production of microelectronic components.
Substrates for microelectronic components e.g. silicon wafers require extremely clean surfaces necessitating repeated cleaning processes (treatments) during manufacture of a chip. The substrate must thereby be cleaned on both sides and at all surface locations. Among physical cleaning processes, wetting procedures are primarily used for single substrate cleaning comprising e.g. brushing, ultrasound, megasound, high-pressure and the like. The substrate must thereby be transported within the cleaning installation to the individual cleaning stations substantially in a wet condition. For single substrate processing, this is normally carried out in a horizontal substrate position using processing robots which e.g. hold the substrate at its lower side using vacuum or sideward clamping or through suitable bearing on transport belts, rollers and the like to facilitate transport. Contact with the surface during handling (both the front side as well as the back side) leads to contamination due to soiling (particles). In addition, the handling systems utilized in these extremely clean rooms are very complicated from a technical point of view and are expensive. The cleaning systems primarily used for the horizontal positioning of the substrate also require, for ever increasing substrate sizes, very large amounts of floor space in the clean rooms, which are consequently very expensive. In addition, collection of particles on the horizontal surfaces of the substrate also occurs in such clean rooms. The incidence of laminar guided clean room air containing residual particles on the large substrate surface leads to substantial contamination of the silicon wafers.
These processes also occur when cleaning rigid discs (metal substrates) or when producing microelectronic components generally referred to as chips on e.g. round silicon wafers using photolithographic processing, wherein the structures are exposed through masks on a photosensitive coating disposed on the surface of the substrate. The photosensitive coating (photo-resist) is thereby spun onto the substrate in a horizontal position, wherein subsequent processing, such as drying of the coating, exposure, development, etching and the like as well as the introduction of bonding agents prior to adding the coating are likewise all carried out in the horizontal substrate position. Handling between individual processing steps is effected using expensive handling robots capable of operation under clean room conditions.
Also known in the art is to spin dry individual wafers in the horizontal position following a wetting treatment. Very high rates of revolution are thereby required (in excess of 1000 to 5000 1/min), since the drops of water located on the wafer following the wetting processes are intrinsically very stable due to their surface tension and bond to the surface in the middle of the substrate. Only low centrifugal forces are active at the center of the substrate so that drying is only possible using very high rates of revolution to achieve sufficient forces in the middle of the substrate. This creates turbulence. Although such turbulence enhances drying, it also stirs-up particles causing contamination of the cleaned surface.
Other drying techniques, e.g. blowing nitrogen onto the middle of the substrate, also produce turbulence having the same effects. Additional warming of the surface (using infrared or laser techniques) can support the drying process. However, evaporation processes thereby occur which result in rinsing water residues in the form of drying spots on the surface of the substrate. These types of drying spots also constitute particles and are undesirable during production of the chips.